There's a lot of things you can sculpt out of the wood from a tree, but in his 2012 exhibition, "The Hidden Life Within," Italian artist Giuseppe Penone sculpted a tree inside a tree!
Photo above via Sphilbrick
Photo: Giuseppe Penone, Cedro di Versailles, 2000-2003 - Artribune
Artist: How do I sculpt a tree?
Teacher: Just remove anything that doesn't look like a tree.
Artist: Well, I guess I'm done, then.